SIPCall - trigger a re-invite on media source change

Changing the media source of a media stream (video in particular)
must trigger a reinvite.
Since currently we do not support changing video properties (resolution
in particular) in the same media session, any changes in the video
properties must trigger a re-invite to restart the media locally and on
the remote peer.

Gitlab: #653

Change-Id: Ibd6192135d272908963cfbc585bec95c66881a28